The present invention relates generally to a road map display system for displaying a rod map and a vehicle driven on the road on a screen. More particularly, the invention relates to a road map display system displaying a vehicle at the center of the display screen and a road map which is displaced on the screen according to the movement of the vehicle.
A display system for displaying the road may and the vehicle position on the displayed road is helpful for the vehicle driver to find his way. A pilot system for a ship is disclosed in the first publication of the Japanese Patent Application Sho 52-159894 (Tokkai Sho 54-89767, published July 17, 1979). In this publication there is shown a method for displaying a sea chart with an indication of the ship position. The sea chart is moved on the display according to the travelling distance and travelling direction of the ship. In this system, coordinates of the displayed sea chart are modified with respect to the ship position and travelling direction of the ship. The sea chart is stored in a digital memory as plotted coordinates. A microcomputer is used for processing modifications of the sea chart coordinate system and for calculation of the ship position based on a sensor, which measures travelling distance and detects the ship direction.
On the other hand, in the automotive vehicle field, Tokkai Sho 52-141662, published on Nov. 26, 1977 shows a map display system for the automotive vehicle. In this system, a microfilm is used to store the map. In this system, the indication of the vehicle position will move in accordance with the travelling distance and vehicle direction.
The present invention is an application of an improvement upon the map display system of the foregoing Tokkai Sho 54-88767 to display a road map for the automotive vehicle driver. For example, the road map display system displays the map in various scales in order to show small roads or small side streets in a town and to alternatively show a wide or larger scale map for use in the country.